Like lebmung wrote, Sour Orange is a fantastic rootstock, as long as the grower does not live in areas susceptible to tristeza virus. Sour Orange has high peel quality, high to very high internal quality, excellent tolerance to Phytophthora, no common incompatibilities except with kumquat & eureka lemon, broad soil adaptation, and as far as it's yield it is generally very similar to that of trees grafted on Carrizo. One interesting point about trees grated on sour orange rootstock. Where tristeza is wide spread, all trees grafted on sour orange will be likely be killed, EXCEPT LEMONS.